My Solution (Plugin-Hack).
qa-plugin/facebook-login/qa-facebook-login.php (L81)
Before: $user=$facebook->api('/me?fields=email,name,verified,location,website,about,picture');
After: $user=$facebook->api('/me?fields=id,email,name,verified,location,website,about,picture,username');
qa-plugin/facebook-login/qa-facebook-login.php (L92)
Before: 'avatar' => strlen(@$user['picture']['data']['url']) ? qa_retrieve_url($user['picture']['data']['url']) : null,
After-1: 'avatar' => strlen(@$user['picture']['data']['url']) ? qa_retrieve_url('https://graph.facebook.com/' . @$user['id'] . '/picture?type=large') : null,
or
After-2: 'avatar' => strlen(@$user['picture']['data']['url']) ? qa_retrieve_url('https://graph.facebook.com/' . @$user['username'] . '/picture?type=large') : null,
Reference pageļ¼
https://developers.facebook.com/docs/reference/api/using-pictures/
$user['picture']['data']['url'] is url of default image ("type=square": 50 * 50 pix)
I am glad if help to Q2A friends.